Low-grade Appendiceal Mucinous Neoplasm and Pseudomyxoma Peritonei: A Case of Appendiceal Mucocele Autoamputation

Low-grade appendiceal mucinous neoplasms (LAMNs) are rare mucin-producing lesions of the appendix, accounting for less than 1% of all gastrointestinal neoplasms. These lesions typically present as a mucocele — a dilated, mucin-filled appendix — either causing an acute appendicitis or detected incidentally on imaging. Perforation of the mucocele can lead to peritoneal mucin deposits, clinically referred to as pseudomyxoma peritonei (PMP). We report a case of a 31-year-old woman, with no significant personal medical history, presenting with lower abdominal pain of several weeks' duration, whose imaging was suspicious for an appendiceal mucocele. The patient underwent a laparoscopic exploration, and an appendiceal mucocele completely amputated from the cecum was identified, along with mucin deposits on the appendiceal serosa, and free mucin within the peritoneal cavity, with a Peritoneal Cancer Index (PCI) >3. Cytological analysis of the mucin was negative for malignant cells, with histological findings compatible with a LAMN. The patient underwent cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Appendiceal auto-amputation represents an exceptionally rare clinical entity, with the literature limited to a small number of reported cases and is even more uncommon when associated with concomitant PMP and LAMN. In the management of these lesions, it is essential to thoroughly inspect the entire peritoneal cavity to exclude or confirm the presence of PMP, as this influences future therapeutic decisions and the overall prognosis.